[NEW DELHI] Excessive withdrawal of groundwater across India is not only lowering the water table, it is also contaminating water with uranium, says a new study.

The study, published last month (May) in Environmental Science & Technology Letters, covered aquifers in 16 of India’s 29 states, with focus on western Rajasthan and Gujarat where uranium concentrations are higher than the WHO (World Health Organization) safe limit of 30 micrograms per litre.

Avner Vengosh, professor of geochemistry and water quality at Duke University, North Carolina, US, and lead author of the study, says that “the decline in groundwater levels accelerates uranium mobilisation to groundwater”.

“The urgent next step is to see if we can identify areas of high prevalence of kidney disease that could be associated with high uranium levels in drinking water”

Avner Vengosh, Duke University

The study also points to the possibility of nitrate pollutants, originating from chemical fertilisers and which makes uranium more soluble (as it is insoluble in its natural form), enhancing the build-up of uranium in groundwater.

India is the world’s largest user of groundwater, with World Bankreporting that more than 60 per cent of irrigated agriculture and 85 per cent of drinking water are dependent on the resource, which is pumped up through borewells.

Vengosh suggests that India’s water agencies make groundwater management a priority to protect people from the ill effects of uranium, which may include chronic kidney disease (CKD). “The urgent next step is to see if we can identify areas of high prevalence of kidney disease that could be associated with high uranium levels in drinking water.”

Sunderrajan Krishnan, executive director of the Inren Foundation, a non-profit water research body based in Gujarat state, said a key finding in the study was the link between water table fluctuations and the presence of uranium. This is especially noticeable when the water level depletes to the point where uranium-bearing rocks in the aquifers are exposed to oxidation.

“Half a century ago, water levels never reached that low,” Krishnan tells SciDev.Net.

The link between CKD and uranium was first made by the state-run Bhabha Atomic Research Centre, Mumbai, says Krishnan. CKD is prevalent in the coastal parts of Andhra Pradesh state.

In the light of the study’s findings it is urgent to make testing for uranium a routine part of the groundwater quality monitoring programme, says Vengosh. Current tests in India include those for arsenic and fluoride, which are among the more serious contaminants that pose risks to human health.